Proportional scale.



N. M. BLAIR. PROPORTIONAL SCALE.

APPLICATION FILED APB.. 19, 1909.

Patented Jan. 11,1910.

MIIIIIIIIII-.IIHZIIIwww@Ikerggergakkbmm @weft for' NELSON lVI. BLAIR, OFNEW ORLEANS, LOUESIANA.

PROPORTIONAL SCALE.

To all whom t may concern.'

Be it known that I, NELSON M. BLAIR, a citizen of the United States,residing at New Orleans, in the parish of Orleans, State of Louisiana,have invented certain new and useful Improvements in ProportionalScales, of which the following is a speciiication.

This invention relates to proportional scales adapted for use bystair-builders, architects, builders generally, and engineers.

The primary object of the invention is to provide a proportional scalehaving independent divisions designating variations in the height orperpendicular extent of stair risers, that may be readily determined bythe application of a measuring instrument with relation to a givendistance and used as a scale one inch per foot and whereby thedimensions or height and number of risers within the given distance maybe readily and accurately ascertained.

The invention consists in the arrangement and combination of aproportional scale having sections varying as to divisions or spacesrepresenting specific fractions of one inch to obtain, in conjunctionwith a. measuring instrument, the number of risers required within agiven distance having a particular or desired perpendicular extent.

The drawing illustrates in plan view a proportional scale embodying thefeatures of the invention.

The proportional scale embodying the features of the invention comprisesfour sections, 1, 2, 3, 4, suitably applied on a base 5 which may beiiexible or rigid and terminally intersect each other to form arectanguiar scale embodying means in the aggregate for obtaining atleast four diiierent measurements and quantities with relation to risersfor stair-building or other uses to which the scale may be applicable.The several sections l, 2, 3 and 4 are arranged in rectangular form andintersect each other to provide an inner space free of markings orinscriptions to provide inner clearance means particularly adjacent tothe inner straight edges of the scales or sections to avoid the leastinterference with the accurate application of a. rule to the said innerstraight edges of the sections. A further advantage in arranging thesections in rectangular form is to render them conveniently accessibleand adjacent so that computations may be easily made in relation to anyone of the sections or comparative cal- Specicaton of Letters Patent.

Application led April 19, 1909.

Patented Jan. 11, 1910. Serial No. 490,844.

culations easily made in relation to two or more of the sections.Furthermore, by having the several scale sections in the same horizontalplane and intersecting each other at right angles to form a rectangle arule may be readily shifted from one scale section to another and thusavoid the necessity of picking up or raising the rule from the surfaceor" the proportional scale as an entirety and thus materially expeditethe operatcr in ascertaining the measurement desired. The section l, forinstance, is divided into a plurality of spaces representingquarter-inches and numbered consecutively from l to 49 7; the section 2is divided into spaces representing seven-twelfths of an inch andnumbered from l to 35 the section 3 is divided into spaces representingve-twelfths of an inch and numbered from l to 29, and the section 4 isdivided into spaces representing three-quarters of an inch and numberedfrom l7 to .27. The actual dimensions are not, of course, shown inconnection with the several spaces of the sections, as it would beimpossible to embody such measurements in the drawing and practicallyillustrate the complete scale. It will also be understood that thesespace measurements may be modied and the number increased or decreased.

In the use of the scale an ordinary rule or other instrument, which canbe used as a scale of one inch per foot, is disposed on the proportionalscale with the ligures which correspond to the space or distance to bedivided touching the inner line of the section to be used or embodyingt-he required number of divisions in accordance with a particularmeasurement in view and with the end of the rule touching or coincidingwith the inner line of the scale space from which the divisions arenumbered. lVith the rule in this position, the required dimensions willbe shown in :tull on the rule at the point where the said rule crosses aline extended from the space or division l2. For example, if thestairway for a twentyfoot story is to be measured, twenty inches on therule corresponds to the measurement of the story as specied, andthirty-four divisions on the scale, for instance as indicated by section2, will indicate the number of risers required in Ythe stairway, and theline of the division or space 12 intersecting the rule will give ininches the heightof the risers when calculated from the end of the ruledisposed atv the beginning of the Scale used.

What is claimed is:

A proportional scale for use in stairbuilding, consisting of ahorizontally vHat base with a pluralityot' scale Sections thereon in thesaine horizontal plane and terniinallT intersecting` at right angles totorni an aggregate scale of rectangular contour and inclosing an innerclear Space to render the inner Straight edges of the scale sectionsclear for the application of a foot-rule thereto, each scale sect-ionbeing divided to designate the nuniber of risers having a particularperpendicular extent and corresponding to a given heightof a support ofa building, each of the scale sections also being divided into spaces ofuniform length Withouty Subdivisions` and the Spaces representing solelyone kind of fractional division of an inch, the Spaces of all of theseetions being consecutively numbered and the spaceS of each sectiondiffering as to length from the spaces ot' the remaining sections andthe nuinber ot' spaces in each section also differing from that of theother sections.

ln testimony whereof l have hereunto Set iny hand in presence of twosubscribing witnesses.

NELSON M. BLAR. VitneSSee:

lV. H. COOK,

ROBERT lvrnmmx

